Background. Relatively few predictors of outcome in first-episode psychosis are potentially malleable and duration of untreated psychosis (DUP) is one. However, the degree to which DUP is mediated by other predictors of outcome is unclear. This study examines the specific effects of DUP on 12-month outcome after adjusting for effects of potential confounders and moderating variables.

Method. The sample comprised 354 first-episode psychosis patients followed up 12-months after remission/stabilization of their psychotic symptoms. Outcome measures included functional outcome, severity of positive symptoms and negative symptoms. Hierarchical multiple regression assessed whether DUP significantly predicted 12-month outcome after adjusting for other predictors. Contrast analysis further clarified the differential effects of DUP on 12-month outcome.

Results. DUP remained a significant predictor of outcome after adjusting for the effects of other variables. This finding remained robust for the subset of patients with schizophrenia or schizophreniform disorder. Functional outcome appeared to decline substantially even after very short treatment delays (>7 days), with more gradual deterioration in functioning until very long DUP (>1 year). Good outcome was variably associated with good pre-morbid adjustment, female gender, diagnosis of affective disorder, short duration of prodromal symptoms, and treatment within the Early Psychosis Prevention and Intervention model in contrast to other models of care.

Conclusions. DUP consistently predicts outcome independently of other variables, and is not simply a proxy for other factors. As one of the few potentially malleable factors influencing outcome, DUP could prove to be a target for secondary preventive efforts in early psychosis.